Induced polarization response of porous media with metallic particles — Part 9: Influence of permafrost

• Published in: GEOPHYSICS
• Main Authors: Revil, André, Razdan, Mridul, Julien, Stéphane, Coperey, Antoine, Abdulsamad, Feras, Ghorbani, Ahmad, Gasquet, Dominique, Sharma, Ravi, Rossi, Magali
• Other Authors: Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement IRD : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols (METIS), Université Pierre et Marie Curie - Paris 6 (UPMC)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Applied Geophysics, Departement de geophysique appliquée, Université Pierre et Marie Curie - Paris 6 (UPMC)-Université Pierre et Marie Curie - Paris 6 (UPMC), Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Ice; permafrost
• Online Access: https://hal.science/hal-02324317; https://hal.science/hal-02324317/document; https://hal.science/hal-02324317/file/2019-Geophysics-Pyrite%20Part%209.pdf; https://doi.org/10.1190/GEO2019-0013.1

International audience We consider a mixture made of dispersed metallic particles immersed into a background material saturated by an electrolyte. Below the freezing temperature (typically 0°C to −4°C), a fraction of the liquid water in the pore space is transformed into ice, whereas the salt remains segregated into the liquid-pore water solution. Our goal is to understand how freezing affects the complex conductivity (induced polarization) of such mixtures. Complex conductivity measurements (96 spectra) are performed in a temperature-controlled bath equipped with a high-precision impedance meter. We cover the temperature range from þ20°C to −15°C to −18°C and the frequency range from 10 −2 Hz to 45 kHz. The spectra are fitted with a double Cole-Cole complex conductivity model. A finite-element model is used to further analyze the mechanisms of polarization by considering an intragrain polarization mechanism for the metallic particles and a change of the conductivity of the background material modeled with an exponential freezing curve. This curve is used to relate the liquid water content to the temperature. In the context of freezing, we test all the aspects of the intragrain polarization model developed in the previous papers of this series, at least for a weakly polarizable background material. The Cole-Cole exponent and the chargeability are observed to be essentially independent of temperature including in freezing conditions. This means that all the relaxation times of the system follow the same temperature dependence and that the chargeability is controlled by the volume fraction of metal. The instantaneous conductivity (high-frequency conductivity) and the relaxation times depend on the temperature in a predictable way, and their product can be considered to be essentially temperature independent. The analytical and numerical models can reproduce the inverse relationship between the relaxation time and the instantaneous conductivity.